1. Field of the Invention
The invention relates to a decoding apparatus and the method thereof of an optical information reproducing system, and more particularly to a decoding apparatus and the method thereof utilizing Viterbi decoding.
2. Description of the Prior Art
Referring to FIG. 1, FIG. 1 is a schematic diagram illustrating a decoding apparatus 10 of a conventional optical information reproducing system (e.g. CD-ROM drive). The decoding apparatus 10 includes an equalizer 12, a Viterbi decoder 14, a demultiplexer 16, a binary array 18, a delay 20, and a reference level generating device 22.
The equalizer 12 is used for receiving a radio frequency signal FRF and outputting an equalization signal Feq with respect to the signal FRF, wherein the signal FRF is related to a pickup head (not shown) retrieving a data (not shown) from an optical information recording medium (not shown), e.g. compact disc. According to a reference level RL, the Viterbi decoder 14 decodes the equalization signal Feq to a digital signal Fbi and outputs the digital signal Fbi. The binary array 18 is used for receiving the feedback of the digital signal Fbi. The delay 20 is used for receiving the feedback of the equalization signal Feq. The demultiplexer 16 is used for respectively receiving the outputs from the binary array 18 and the delay 20, and, according to the output of the binary array 18, selectively inputting the output of the delay 20 into a corresponding low-pass filter 222 of the reference level generating device 22. Afterward, the reference level generating device 22 will generate the reference level RL.
In the decoding apparatus 10 of the conventional optical information reproducing system, once the optical information recording medium (e.g. CD) is damaged, such as scratch, finger print, etc. The data stored in the damaged area and read by the pickup head are incorrect data. Accordingly, the reference level generating apparatus 22 will generate an incorrect reference level RL, so that the Viterbi decoder 14 will decode the data to incorrect information.
Moreover, in the decoding apparatus 10 of the conventional optical information reproducing system, N calculators are needed to calculate N reference levels. In other words, it had not been seen in the prior art about that sharing less than N calculators to calculate N reference levels.